public class test09 {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>> res = new ArrayList<>();
        Arrays.sort(nums);
        for(int i = 0;i<nums.length;i++){
            if(nums[i]>0 && nums[i]>target){
                return res;
            }
            if(i>0 && nums[i]==nums[i-1]){
                continue;
            }
            for(int j = i+1;j<nums.length;j++){
                if(j>i+1 && nums[j]==nums[j-1]){
                    continue;
                }
                int left = j+1,right = nums.length-1;
                while(left<right){
                    int sum = nums[i]+nums[j]+nums[left]+nums[right];
                    if(sum>target){
                        right--;
                    }else if(sum<target){
                        left++;
                    }else{
                        res.add(Arrays.asList(nums[i],nums[j],nums[left],nums[right]));
                        while(left<right && nums[left]==nums[left+1])left++;
                        while(left<right && nums[right]==nums[right-1])right--;
                        left++;
                        right--;
                    }
                }
            }
        }
        return res;
    }
}
